NASA’s $2.5-billion Curiosity rover safely landed on Mars early Monday morning, kicking off its two-year journey to determine if Mars ever harbored live or could sustain life in the future. The one-ton rover is equipped with a suite of advanced science instruments designed to gather information about the habitability of Mars. This includes a sensor called the Radiation Assessment Detector, or “RAD,” which was installed on the six-wheeled rover to measure radiation such as cosmic rays and solar particles passing through the Martian atmosphere. RAD is an extremely important little piece of equipment because it will help scientists determine what kind of radiation astronauts would be exposed in future manned missions to Mars.

But the toaster-size instrument was also useful during Curiosity’s nine-month journey to the Red Planet. The detector was placed inside the spacecraft that Curiosity was riding. The rover’s location in the belly of the spacecraft is similar to where an astronaut would be sitting, therefore “exposing itself to the same cosmic radiation humans would experience following the same route to Mars1,” says NASA.

So how well did the spacecraft protect Curiosity from deep space radiation?

According to RAD’s principal investigator Dan Hassler, “Only the strongest radiation storms have made it inside. Moreover, charged particles penetrating the hull have been slowed down and fragmented by their interaction with the spacecraft’s metal skin.”

This is vital information to prepare for future human exploration. RAD will continue to collect data about high-energy radiation on Mars over the next 687 days on the planet.